Oil burner fuel control



June 19, 1945. w. 0.

B-EHRENS 2 37 OIL BURNER FUEL CONTROL Filed March 6, 1941 MOTOB SUCFIONLINE FROM TANK BURNER CIIZCULATING/ Pump VA L V5 i RETURN TO TANKEven/92 Patented June 19, 1945 UNITED STATES PATENT OFFICE on. BURNERFUELCONTROL William 0. Behrens, Harvey, 111. Application March 6, 1941,Serial No. 381,949

2 Claims.

The invention relates to oil burners and more particularlyto means forcontrolling the flow of fuel oil to the nozzle of an oil burner of thevariable capacity type.

It is a general object of the invention to provide a novel fuel oilcontrol circuit which is characterized by its extreme simplicity, yetwhich is capable of exceptional performance in the dea furnace.

This mechanism, which constitutes no part of the present invention, maybe of the general type illustrated and described in'my Patent No. 2,202,822, its primary function being to discharge a stream of air and finelyatomized fuel oil into To this end, it may include an electric motor ll(Fig. 2) which drives a blower (not shown) for delivering forced draftcombustion air to the region of a fuel oil atomizer l2, which may alsobe suitably actuated by the burner motor. An air damper I3 is interposedin the path of the air flow to the region of the atomizer It is afurther object of theinvention to provide a novel oil flow circuit for aburner which assures proper combustion air supply during starting andprovides smooth ignition.

It is a still further object of the invention to provide new andimproved apparatus of this type capable of supplying high viscosity fueloils to a burner over a wide range of capacities and temperatures and atthe same time'maintaining a constant oil-air ratio adjustment.

Other objects and advantages will'become apparent as the followingdescription proceeds taken in connection with the accompanying drawingin which:

Figure 1 is a perspective view of an -oil burner having associatedtherewith an oil fiow control circuit incorporating the features of thepresent invention.

Fig. 2 is a diagrammatic view of control circuit shown in Fig. 1.

While th invention is susceptible of various modifications andalternative constructions, I

the oil flow have shown in the drawing and will herein describe indetail, the preferred embodiment, but

it is to be understood that I do not thereby intend i to limit theinvention to the specific form disclosed, but intend to cover allmodifications and alternative constructions falling within the spiritand scope, of the invention a expressed in the appended claims.

Referring more particularly to Fig. 1 of the drawing, I have illustratedgenerally therein merely for purposes of disclosure one form of fuel oilburner adapted for use in connection with the and is adjustable by meansindicated at M to regulate the quantity of combustion air supplied inaccordance with the kind'and amount of fuel oil delivered. A fuel oilsupply line l5 enters throughthe rear wall of the burner housing and maybe suitably connected to deliver variable quantities of oil to theatomizer located at the front of the burner.

In an oil burner of this type, it is essential that the ratio of fueloil and combustion air supplied to the combustion chamber be regulatedaccurately for eflicient combustion over various capacity ranges. Inother words, when the amount of fuel oil delivered to the burner isincreased, a proportionate increase in the supply of combustion air mustbe provided. Accordingly, provision is ordinarily made for conjointcontrol of fuel and air so that a substantially constant ratio may bemaintained in increasing or decreasing the rate of oil delivery to theburner. In burning oils of low viscosity under uniform temperatureconditions, not giving rise t variations in viscosity, the problem ofmaintainin a substantially constant fuel-air ratio is relatively simple.through ordinary metering valves effecting a mere throttling operationwhich may be made substantially proportionate to a similar throttling ofthe combustion air. Considerable difficulty is encountered, however, inattempting to meter or throttle oils, particularly those of heavyviscosity,

varying capacity ranges.

fuel oil flow control circuit of the present invention. In the presentinstance therperspective view (Fig. 1), taken from the rearand at oneside of the apparatus, illustrates a burner housing H! which enclosesthe burner mechanism.

One rather costly and complicated solution which has been suggestedheretofore-for metering fuel oil over varying temperature ranges is theprovision of a so-called viscosity metering valve. A valve of this typei adjustable automaticallyfor changes in viscosity, the adjustment beingresponsive to changes in the oil pressure.

In other words, when the temperature of the oil Variable quantities maybe supplied supply is readily available.

is raised the pressure is decreased due to a lower viscosity, and whenthe oil is cold, the viscosity ,being higher, the pressure iscorrespondingly higher. In such installations the valve orifice isautomatically enlarged or diminished as the oil pressure changes inresponse to changes in temperature. Viscosity metering valves have notbeen found wholly satisfactory, however, for the reason that theautomatic adjustment for viscosity changes, responsive to oil' pressure,cannot be made correctly proportional to attain a constant oil-air ratioover different capacity ranges. An adjustment which is correct in onerange of burner capacity is not correct for another range. In otherwords, assuming that the viscosity metering valve is so constructed asto provide a proper adjustment for changes in viscosity when the burneris operating at full capacity, the valve will be incapable ofcompensating for viscosity changes in lower ranges of capacity or whenthe valve has been throttled. Similarly, in burning fuel oils of variousspecific viscosities in the same installation, an adjustment which willcorrectly compensate for variations due to temperature' changes for oneoil will not correctly compensate for another oil of a dilTerentspecific viscosity.

The importance of maintaining a substantially constant fuel air ratioisemphasized in industrial burners where large quantities of highviscosity oils are utilized as fuel over long periods of time. Undersuch circumstances, lazy or smoky fires in the combustion chambersresult in carbon formation, reduced burner capacities and inemcient fuelconsumption. I have accordingly provided an extremely simple apparatusfor delivering variable, yet precise quantities of fuel oil to theatomizer of an oil burner over wide ranges of capacity, oil viscosityand temperature conditions. The system utilizes a positively operatedadjustable metering pump in conjunction with means such as a circulatingpump or gravity feed for assuring, at all times and under all conditionsof temperature and oil viscosity, an ample and readily available supplyof oil for the metering pump.

In the present instance, the apparatus comprises a circulating pump 16drivingly connected with the burner motor. II and adapted to draw oilfrom a suitable source of supply through a conduit line I! hereinillustrated as passing through a hinge l8 of the burner front plate. Thecirculating pump delivers oil under a substantially constant pressure toan adjustable metering pump I 9 through suitable oil lines 20 and 2|. Onthe delivery side of the circulating pump a simple by-pass or bleeder 22is provided for the return passage of excess fuel oil to the sourcethrough a conduit oil line 23 which may be arranged to pass through thelower hinge of the burner front plate. The metering pump may be of anysuitable type capable of delivering positively a specific volume of fueloil to the oil line l regardless of its viscosity, provided an amplePreferably, the pump is 'of the rotary, radially slidable vane typewhere in provision is made for varying the eccentricity of the pumpingchamber relative to the rotor provided for carrying the'radiallyslidablevanes. The details of construction of a metering p mp suitablefor the purpose,but constituting no part of the present invention, aredisclosed in my Patent No. 2,302,411, issued November 17, 1942. Asillustrated in Fig. 1 of the drawing, an adjusting shaft 24 extendsaxially from the metering pump housing and is adapted for conjointinterrupt the flow after ,the circuit is pump to the proper quantity ofcombustion actuation with the air damper adjusting means l4 through theagency of a rod 25. The metering pump may be suitably driven from theburner drive shaft 26 through such means as worm gearing 21.

It will'be apparent that the circulating pump I 6 which is driven fromthe burner motor will provide a constant and ample supply of fuel oilfor the metering pump l9 under all operating conditions, regardless ofvariations in oil viscosity due to temperature changes and irrespectiveof the type or grade of oil burned. With this ample and readilyavailable supply the metering pump l9, also driven from the burnermotor, will be capable of delivering exactly the same quantity of oilfor any given setting irrespective of'variations in oil viscosity andtemperature. The me- .tering pump will be subject to no variable andfluctuating back pressures to impair the accuracy a circulating and ametering pump is the elimination of troublesome and costly relief valveswhich must be utilized in connection with viscosity metering valves.Since metering valves of this type require pressure in order to meterthe oil,

a simple T by-pass for the relief of excess oil is not operative.Similarly the arrangement has marked advantages over prior art systemsutilizing needle valves which have a'tendency to gum up and clog incontinuous service.

Means for positively stopping the oil flow when the burner is shut down,in the' present instance, comprises a solenoid operated shut-off valve28 located in the oil line 20-21 between the metering pump and thecirculating pump and ahead of the by-pass 22. To actuate the valve, itssolenoid is connected in the burner motor circuit 29, 30 by conductors3|, 32 for'concurrent energization with the burner motor. The valve 28is located on the suction side of the metering pump and, since it iswired in the motor circuit, it will close instantly when the burner isshut down to of oil between the circulating pump and the metering pump.The burner motor II, and accordingly the metering pump N, has a periodof overrun of approximately 30 seconds intake is closed, substantiallyall fuel oil is exhausted from the pump during this overrun. The smallamount of oil remaining in the discharge pipe or line l5 drains into thehot burner and is consumed before the burner cools. After-flow orso-called after-dribble" of oil from the nozzle, following the coolingdown of the burner, is thus eliminated and carbon formation around thenozzle and atomizer is materially reduced.

An inherent characteristic of the present arrangement is a time delay ofapproximately 15 seconds after starting the burner, before the oilreaches the atomizer, since the oil line from the burner nozzle as wellas the' pump chamber must be refilled. Expensive relays'with built-intime delay mechanisms which have been frequently provided to accomplishthis end are thereby eliminated and fully atomized oil with a air issupplied to effect a-smooth ignition without puffs or "flashback."rthermore in burning extr ely heavy or high viscosity oils wherepreheating of the oil opened and, since the pump able with heavy fueloils to insure tight closure of the valve.

' starting normally encountered after the burner has been idle for aperiod of time. It will be seen also that the valve 28 is constructed sothat the suction of the metering pump will facilitate its closing.During the overrun period of the metering pump after the control circuitis broken, the

- suction created'in the line between the solenoid valve and themetering pump is especially valua rapid and Thus, the use or a lighterweight and less powerful solenoid is permitted.

I claim as myinvention:

' l. The combination withan oil burner of the type having power drivencombustion air supply means, of an electric motor arranged to drive theair supply means, an operating circuit for said motor, a metering pumpdriven by said motor operative to deliver fuel oil to the burner at apredetermined rate, means for delivering a readily available supply offuel oil to the intake of said metering pump, a shut-off valveinterposed'in the intake of said metering pump, a solenoid connected inthe motor circuit and operative to open said valve when the motorcircuit is closed and to close said valve when the motor circuit isopen, said motor adapted to coast for an interval following the openingof its circuit and the closure of said shut-off valve wherebysubstantially all fuel oil is exhausted from said pump, the filling ofsaid pump upon the starting of the motor acting to interpose a delay inthe delivery of fuel oil to the burner whereby to insure an adequate airsupply for starting the burner.

- 2. The combination with an oil burner of the type having an atomizerlocated in close prox imity to the combustion zone of the burner, meanszone, an electric motor arranged to drive said air supply means, ametering pump driven by said I motor and adapted to deliver fuel oildirectly to said atomizer at a predetermined rate, a circulating pumpdriven by said motor and adapted to deliver fuel oil to the intake ofsaid metering pump, a shut-oil valve interposed between said circulatingand metering pumps, a solenoid adapted when energized when deenergizedto permit the valve to close, means connecting said solenoid in circuitwith said motor whereby said solenoid is energized when the motorcircuit is closed and deenergized when the motor circuit is opened, saidmotor adapted to coast for an interval following the opening of itscircuit whereby said metering pump is enabled to assist in closing saidvalve and to completely empty its chambers of fuel oil so as to preventany flow or 011 while the burner is shut down, the filling of thechambers of said pump upon the subsequent starting of said motor servingto interpose a delay in the delivery or fuel oil to the atomizer andthereby insure an adequate air supply for starting the burner.

, WILLIAM O. BEHRENS.

for supplying combustion air to said combustion to open said valve and

